This invention relates to a hydraulic, variable displacement, axial piston machine. More particularly, it relates to an improved means for damping vibration producing forces within the machine which includes an improved means for mounting a pivoting yoke which supports a swash plate.
Variable displacement axial piston machines in which the swash plate is mounted on a pivoting yoke are well known. In such a machine it is common for the yoke pivots to absorb all of the hydraulic forces generated during operation of the machine, i.e., the axial and radial forces. The yoke pivots may be mounted in antifriction bearings or have hydrostatic bearings.
Among the problems with antifriction bearings are, they are expensive and due to bearing clearance requirements and the resulting concentrated load on the outer ring, they cannot be utilized in accordance with their theoretical static load capacity. This necessitates the use of a larger, more expensive bearing. Additionally, the vibrations from and the forces of the machine lead to premature material fatigue in the rolling contact zone unless the bearings are oversized with respect to service life.
Hydrostatic bearings for yoke pivots are disadvantageous in that they leak fluid, have widely varying friction ratios and require relatively high adjusting forces which, in turn, lead to more costly control devices for adjusting the yoke.
It is desirable to provide a variable displacement, axial piston machine in which the pivots for the yoke do not absorb the forces which act on the swash plate and in which vibrations are damped or otherwise reduced to thereby reduce the size and cost of pump components and increase the life of the pump.